Ship pod-mounted hydrojet propeller unit driven by a hollow electric motor

ABSTRACT

The hydrojet boat submerged propulsions system is low noise and has good output.  
     It comprises principally a hydrojet propulsion system comprised of a hydraulic screw ( 7 ) feeding a helico-axial pump ( 8 ) emerging through downstream guide vanes ( 9 ). A nozzle ( 10 ) completes the assembly, which is supplied by lateral intakes ( 6 ). The electrical motor ( 11 R,  11 S) is represented axially, but can also be radial. The shaft ( 3 ) is rotationally mounted by means of hydraulic thrust bearings ( 4 V,  4 R). The system can be oriented in azimuth.  
     Application in ship and submarine propulsion.

FIELD OF THE INVENTION

[0001] The invention relates to the field of ship propulsion, bothsubmersible and non-submersible, by means of immersed engines on theoutside of the hull, under or alongside the hell of a submersible ship,for example, such as a boat, or on any side of the hull of a submarine.More particularly, it relates to such a propelling means by means ofhydrojet driven by an electric motor.

PRIOR ART AND STATEMENT OF THE PROBLEM

[0002] In the field of ship propulsion, whether submersible ornon-submersible, it is known to use several propulsion methodsimplementing these completely immersed propulsion pods. Of these, thepropulsion method by hydraulic jets commonly known as “hydrojets” can bementioned. This type of method is represented by the French patentapplication filed by this applicant and published under number 2 765262. This technique employs the reaction principle, the water beingaspirated through a water intake arranged in front of the pod. A highoutput pump, arranged within said latter, communicates energy to thewater for the engine on the outside in the form of a jet, through atube, thus creating a thrust that propels the watercraft. Such a pod canbe oriented in azimuth and consequently the direction can be choosen byrotating the pod. This type of engine thus makes it possible for awatercraft to execute any maneuver in port, to stabilize itself en routeor to effect dynamic positioning without the utilization of anothermechanism. This type of pod can also be oriented about a horizontal axisin order to allow change of attitude or the depth of a submarine.

[0003] On the one hand, in a second type of propulsion by immersed pod,French patent application filed by this applicant under number 2 768 119can be mentioned, wherein a naval engine with a centrally disposedpropeller and an asynchronous discoid motor. This type of engine iscomprised principally of a central hub surrounded by the vanes of animpeller, around which the electrical rotor is fixed in discoid fashionand a bushing holding bearings. The stator is arranged at either end ofthe electric rotor, around bearings. In other words, the electricalmotor surrounds the tubing, inside of which the impeller is arranged andthrough which the water flow passes. However, this type of engine doesnot provide outstanding performance, is very noisy and is susceptible tocavitation problems.

[0004] The purpose of the invention is to provide a third type of navalengine that is immersed and placed in a pod, eliminating the drawbacksassociated with the two known types of engines.

DESCRIPTION OF THE INVENTION

[0005] The main object of the invention is, then, a ship engine, in apod, utilizing both the hydrojet method and propulsion by means of ahollow electrical motor that is, surrounding the propelling hydraulicelements and the propulsed water flow. It comprises principally a pod,within which the following elements are arranged:

[0006] an electrical motor,

[0007] an rotating engine assembly driven by the electrical motor;

[0008] an outlet nozzle fixed to the rear of the pod downstream of therotating engine assembly, and

[0009] the guide vanes fixed to the pod.

[0010] The engine according to the invention is characterized in thatthe rotating engine assembly is comprised of:

[0011] a hydraulic screw, and

[0012] a helico-axial pump arranged upstream and integrally to thehydraulic screw, and

[0013] as the electrical motor is of the hollow type; that is, having arotor and a stator having a relatively wide diameter and hollow in itscentral part, such that it surrounds the rotating engine assembly, sothat the rotor is fixed around the rotating engine assembly, in order todrive it in rotation.

[0014] In the preferred embodiment of the invention, the motor rotor isarranged around the hydraulic screw.

[0015] In order to allow the water to reach the interior of the pod, inparticular upstream of the hydraulic screw, it is proposed that intakeopenings be provided on the sides thereof.

[0016] In the principle mechanical realization of the rotating engineassembly, which is counted on a shaft, itself mounted rotationally inthe pod by means of hydraulic thrust bearings.

[0017] According to the invention, the electrical motor can be of twotypes: a first type that is of the radial field type, the motor having awide exterior diameter; the second type being the axial field type andhaving the same inside diameter, but of greater length.

LIST OF FIGURES

[0018] The invention and its different technical features will be betterunderstood in reading the following description, provided by way ofexample, and illustrated in two figures each representing, respectively:

[0019]FIG. 1 representing in cross-section a first embodiment of theengine according to the invention, equipped with an axial electricalmotor, and

[0020]FIG. 2 representing in cross-section a second embodiment of theengine according to the invention, equipped with a radial electricalmotor.

DETAILED DESCRIPTION OF THE TWO REALIZATIONS OF THE INVENTION

[0021]FIG. 1 represents the engine according to the invention andequipped with an axial field electrical motor; that is, having a moreelongated form around the axis 1 of the engine. On the inside of a pod 2a shaft 3 is mounted rotationally by means of hydraulic thrust bearings4V and 4R, each mounted in a forward part 2V and a rearward part 2R,respectively, of the pod 2. At the front end 3V of the shaft; in otherwords, downstream of the front part 2V or the pod, an intake chamber 5equipped with several intakes 6 arranged laterally relative to the axis1 of the engine. The water is then aspirated through said intakes 6 inorder to reach the inlet of a rotating engine assembly supported by theshaft 3.

[0022] An hydraulic screw 7 is affixed around said latter. At the outletof said later, the internal form of the pod 2 widens in order to form atorically domed chamber around the rear part 2R of the pod 2. The vanes8 of a helico-axial pump, integral with the shaft 3, are arranged in theexpanding first part of the domed chamber. They are followed, in thesecond part that abuts the domed chamber, by the guide vanes 9 affixedto the pod 2. The hydraulic circuit of the engine is completed by anozzle 10 affixed to the pod 2.

[0023] The electrical motor is of the water—immersed type and isarranged axially around the hydraulic screw 7. The stator 11S isintegral with the pod 2, while the rotor 11R is fixed around thehydraulic screw 7 and is integrated on the rotating propulsion assembly.The stator 11S and the rotor 11R are sheathed. The motor can be eithersynchronous or asynchronous.

[0024] The thrust bearings 4V and 4R are of the hydraulic type; moreprecisely, they are supplied continuously with the water in which thepod is situated, under pressure.

[0025]FIG. 2 represents the engine according to the invention in anembodiment utilizing a radial type motor; in other words, the electricalfield is radial. Accordingly, its exterior diameter is somewhat greaterthan that of the axial motor used in the embodiment described withreference to FIG. 1. In contrast, its length is shorter.

[0026] The pod 12 is similar to the pod 2 of FIG. 1 and the rotatingengine assembly is virtually identical. The screw, the vanes 8 of thehelico-axial pump, the guide vanes 9 and the nozzle 10 are identical.The same applies to the shaft 3 of the rotating engine assembly, whichis similarly mounted rotationally by means of thrust bearings 4V and 4Rin the front part 12V and rear part 12R, respectively, in the pod.

[0027] In contrast, the start of the hydraulic travel is somewhatdifferent in the sense that the entry chamber 15 is somewhat moreelongated, intake openings 16 being equally placed-laterally, however.

[0028] The motor thus comprises a rotor 21R in discoid form fixed aroundthe hydraulic screw 17. It is placed between the two parts 21S of thestator that are fixed relative to the pod 12.

[0029] Advantages of the Engine According to the Invention

[0030] Several advantages are inherent to the hydrojet propulsionmethod. In fact, at equal power, a propeller engine turns at about 150r.p.m., while a hydrojet engine turns at about 600 r.p.m. The size ofthe motor being inversely proportional to the rotational speed, themotor used in the hydrojet method is much more compact than thatutilized for driving a propeller.

[0031] It is advantageous to couple on the same pod two engines; that istwo hydrojet systems. In fact, this makes it possible to eliminate thetorque stresses on the orientation system of the pod if the two groupsoperate in counter-rotation; that is, the one in detrogyral rotation andthe other in sinistrogyral rotation, the two torques canceling eachother.

[0032] At high speed, the propeller engines have a tendency to undergocavitation. This phenomenon causes noise and risks damaging the blades,in contrast with the hydrojet propulsion system, which does notcavitate.

[0033] The use of hydraulic thrust bearing makes it possible to avoidusing ball bearings. This reinforces resistance to impact, especiallymilitary impacts.

[0034] From the point of view of acoustic discretion, hydrojetpropulsion has a number of advantages. In fact, the type of pump, thespeed, the fact that it is force fed by a hydraulic screw and that thewater flow is done in a confined channel are advantages with respect tothe propeller that turns in an exposed environment and at low frequency.The same applies to the utilization of hydraulic thrust bearingsreplacing ball bearings, which by nature are noisy.

[0035] The engine according to the invention does not require accessoryventilation, lubrication or cooling. The reverse of thrust is done as inthe classical hydrojets using a concave deflector, maneuvered by a servoactuator.

[0036] The performance of a helico-axial pump used in the engineaccording to the invention and associated with a hydraulic screw thatfeeds the input of the helico-axial pump, is of the order of 75%. A 10%increase in performance can be anticipated relative to a traditionalpropeller.

[0037] Utilization of a hydrojet engine and in particular a doublehydrojet, can be conveniently integrated into the water lines and in theunderwater hull of the ship. In this case, it protrudes less than apropeller engine, detached from the hull of the ship in a pod mounted atthe end of a mast. The hydraulic drag and the tactical vulnerability isthus considerably reduced.

[0038] It is possible to use four engines according to the invention onthe same adjustable platform; this solution favors integration into theunderwater hull.

1. A ship's hydrojet engine arranged in a pod and utilizing anelectrical motor, comprising: a pod (2, 12); an electrical motor (11R,11S, 21R, 21S) arranged in the pod; a rotating engine assembly (16, 17,8, 9) driven by the rotor of the electrical motor, and an outlet nozzle(10), fixed to the rear of the pod (2, 12), downstream of the rotatingengine assembly, and guide vanes (9) fixed to the pod (2, 12),characterized in that the rotating engine assembly comprises a hydraulicscrew (7, 17) and a helico-axial pump (8) placed downstream and integralwith the hydraulic screw (7, 17) and in that the electrical motor is ofthe hollow type that is, having a wide diameter rotor (1R, 21R) and astator (11S, 21S) and hollow in its central part in order to surroundthe rotating engine assembly and so that the rotor (11R, 11S) is fixedaround the rotating engine assembly.
 2. The ship's engine according toclaim 1, wherein the rotor (11R, 11S) is placed around the hydraulicscrew (7, 17).
 3. The ship's engine according to claim 1, wherein itcomprises lateral intakes (6, 16) for entry of the water into therotating engine assembly.
 4. The ship's engine according to claim 1,wherein the rotating engine assembly is mounted on a shaft (3) mountedrotationally in the pod (12) by means of hydraulic thrust bearings (4V,4R).
 5. The ship's engine according to claim 1, wherein the electricalmotor (11R, 11S) is of the axial field type.
 6. The ship's engineaccording to claim 1, wherein the electrical motor (21R, 21S) is of theradial field type.